c-Jun Protein Expression and Seizure-induced Neuronal Damage on Hippocampal Explant Cultures of Rat in Different Maturation Stage

ABSTRACT

PURPOSE: Immaure brain is more resistant to seizure-induced neuronal damage than the adult brain in animal study. Immediate early genes such as c-jun play a critical role in neuronal damage. Therefore, we hypothesized that the difference of constitutive and electrically stimulated c-Jun expression would explain the difference in neuronal damage from seizures between immature and mature explant culture. METHODS: Seven and 14 days-in-vitro(DIV) hippocampal explant cultures derived from 8-day-old rat pups were used. Extracellular field recording was done in cultures. A 1-sec stimulus train(60 Hz, 0.1 msec rectangular pulses) was applied to the Schaffer collaterals, and the afterdischarge was recorded in CA1 pyramidal layer. Cultures were returned to the incubator and observed serially. Intensity of propidium iodide fluorescence indicative of neuronal damage was quantitated as percent of total damage induced by 2 mM NMDA. Proteins extracted from individual cultures were analyzed by Western blot. RESULTS: Constitutive c-Jun protein expression at 7 DIV was higher than that at 14 DIV. There was not a significant difference of c-Jun expression between the 7 DIV and 14 DIV cultures after electrical stimulation. Neuronal damage after electrical stimulation in the hippocampus at 7 DIV was significantly lower than at 14 DIV. CONCLUSION: The results show reduced neuronal injury from seizures in more immature culture. However, constitutive expression of c-Jun protein was higher. Higher constitutive expression may inhibit further induction of c-Jun from seizures and thus result in less severe neuronal injury.